42.20 km + 12.82 km =
55.02 km
55.05 km
55.07 km
55.00 km
42.20 km + 12.82 km = 55.02 km
If a1,a2,a3,a4 are in AP, then
AA
×A A––––––––––––
+AA×––––––––––
ABA–––––––––––